title: Cerebral columnar organization of the first nociceptive component induced by CO2 laser on the tail of the rat.
abstract: The somatotopic map of the first nociceptive component in the primary somatosensory cortex (S1) is still unclear. In this study, a CO(2) laser was applied to the tail of the rat to induce nociception without the interference from large myelinated (A(beta)) fibers. Thus, only noxious fibers could be activated. Two-dimensional current-source-density analysis was used to analyze the evoked field potentials. Using this method, the nociceptive responses of A(delta)-fibers in S1 were verified, and the somatotopic map of the first nociceptive component in S1 was identified. We found that whether light touch or laser-induced nociception was applied to the tail of the rat, the responsive topography in S1 was consistent. Discrimination of these two modalities was achieved vertically in the same column; the deeper layer represented the nociceptive response while the superficial layer encoded the response to light touch. This is quite different from that of a primate brain.
authors.affiliation: Institute of Biomedical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan. jaw@ntu.edu.tw
authors.forename: F-S
authors.initials: FS
authors.lastname: Jaw
authors.forename: Y-C
authors.initials: YC
authors.lastname: Kao
authors.forename: C-P
authors.initials: CP
authors.lastname: Chen
authors.forename: W-L
authors.initials: WL
authors.lastname: Liao
mesh_terms: D000818:Animals; D001931:Brain Mapping; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000528:radiation effects; D054020:Lasers, Gas / Q000009:adverse effects*; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009431:Neural Conduction / Q000528:radiation effects; D010146:Pain / Q000209:etiology* / Q000473:pathology*; D010147:Pain Measurement; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013623:Tail / Q000294:innervation / Q000528:radiation effects*